Maybe you could make a fake fairy, put an LED or something in it and use it as a bottled fairy desklight sort of thing?

I was thinking a fairy also.

__________________"The time has come," the Walrus said, "to talk of many things. Of ships, and shoes, and ceiling wax. Of cabbages and kings. And why the sea is boiling hot and whether pigs have wings."

@Kuroki: I was really looking for something anime or video game inspired, so I'm avoiding turning such a neat bottle into a simple vase.

@Bisected & PrincessKaori: I thought of a fairy too, but the opening/neck of the bottle is really small. Do you think it'd look funny if the fairy was so tiny? As I recall...weren't the fairies kinda large in relation to the bottles?

@generally everyone else: So...silly question. If I make a potion, any suggestions on what liquid or material I should use so that the thing doesn't gain mold if I just leave it on my desk?

@Kuroki: I was really looking for something anime or video game inspired, so I'm avoiding turning such a neat bottle into a simple vase.

@Bisected & PrincessKaori: I thought of a fairy too, but the opening/neck of the bottle is really small. Do you think it'd look funny if the fairy was so tiny? As I recall...weren't the fairies kinda large in relation to the bottles?

@generally everyone else: So...silly question. If I make a potion, any suggestions on what liquid or material I should use so that the thing doesn't gain mold if I just leave it on my desk?

Technically, I think most of the fairies' bulk was made up of their glow (since they're just balls of light in the 3D games). That's why I suggested using an LED.

If you want to make a potion, I'd use water with food colouring or paint and a bit of disinfectant (just to make sure nothing grows in it).